The activation of jack-bean arginase by cobalt, manganese, and iron

bited this inactivation.The concentrations of pantoyltaurine required for inhibition of the pantothenate metabolism by different organisms varied over a 300-fold range but were correlated with the concentrations required for inhibition of growth of the respective organisms.2. Of 14 compounds structurally related to panto- thenate, seven, which inhibited growth of haemolytic.streptococci, inhibited their inactivation of pantothenate.The activities of the compounds in inhibiting the inactivation of pantothenate were correlated with their activities in inhibiting growth.Five compounds affected neither process; two com- pounds which inhibited growth and which were not antagonized by pantothenate did not affect panto- thenate inactivation.3. Of the compounds examined, those which in- hibited pantothenate inactivation were all amides of pantoic acid; those not containing an intact and unsubstituted pantoia acid portion did not affect pantothenate inactivation.We are greatly indebted to Drs Barnett and Robinson, and to Dr Swain, for gifts of pantothenate analogues;-to the Department of Bacteriology of this University for bac- terial strains, and to Miss L. Whipple for assistance during the development of the assay method.